Motivational interviewing (MI) is a directive, client-centered therapeutic method employed in the treatment of substance abuse, with strong evidence of effectiveness. To date, the sole mechanism of action in MI with any consistent empirical support is change talk (CT), which is generally defined as in-session verbal commitments by clients to change their problem behavior. Sustain talk (ST) incorporates verbal commitments to maintain the status quo. MI maintains that during addiction treatment clients essentially talk themselves into change. Multiple studies have supported this theory, revealing that the frequency and strength of these change talk utterances from MI treatment sessions predict substance use outcomes. Although a causal chain has now been established linking therapist speech, client change talk, and substance use outcomes, the neural substrate of change talk remains largely uncharted. This K01 proposal is designed to explore that neural substrate. Building upon the results of studies of causal mechanisms in motivational interviewing, this application represents an effort to identify biologically-based processes that underlie client change talk during treatment sessions, with the long-term goal of understanding how it might be more efficiently and powerfully elicited to improve substance abuse outcomes. Furthermore, this study is designed to provide important training to prepare me for a career as an independent clinical scientist. My immediate career goals are to: (1) acquire expert-level knowledge about endophenotypes in alcohol use disorders, (2) deepen my knowledge about advanced analysis methodologies including network- level functional neuroimaging analysis and longitudinal data analysis, and (3) develop my scientific and grant writing skills. My overarching goal is to become an independent clinical scientist and a leader in the application of neuroimaging methodologies to study mechanisms of behavior change in substance abuse treatment. Under the guidance of a mentoring team led by Dr. Barbara McCrady and including Dr. Vince Calhoun, Dr. Theresa Moyers, and Dr. Claudia Tesche, I will explore the neural substrate of change talk during an actual MI session using magnetoencephalography (MEG) in a sample of ambivalent alcohol users. In subsequent measurement sessions I will use MEG to measure brain responses to brief utterances of the client's own change talk and sustain talk recorded from that MI session. In this way I can explore differences between brain activity measured when change talk is originally expressed within an MI session, and that measured in follow- up measurements using recordings of the client's change talk. I will also examine differences in brain activity between change talk and sustain talk using independent component analysis, and test for relationships between brain activity and substance use outcomes. In the long term this information could be used to develop refinements to motivational interviewing, targeting the salient brain regions and processes more precisely in order to achieve the most efficient and powerful expressions of change talk, which could ultimately lead to improved substance abuse outcomes.